Method of and means for testing telegraph transmission



Nov. 19, 1929. E. F; WATSON El AL 1,735,943

METHOD OF AND MEANS FOR TESTING TELEGRAPH TRANSMISSION Filed Jan. 1928 Il -ll ags QENQM w 35% m5 53k ATTORNEY UNITED STATS Patented Nov. 19, 1929 EDWAR ID FISK WATSON, or LARCHMONT, LAND- BURDETTE- STEVENS swEzEY, or FLORAL PARK, NEW YORK, ASSIGNORS TO AMERICAN TELEPHONE ANDYTELEGRAPH COMPANSLACORPORATIONOF NEW YORK p I A METHOD or Ann MEAns r1012. 'rnsrrne rnnnealirn rRANs IssIoN Application filed January 20, 1928 i This invention relates to telegraph systems, and more particularly to improvements 1n methods of and'means for measuring telegraph transmission by employin'g'dlstorted signals rather than perfect signals.

Informer methods of measuring'telegraph transmission, which have been utilized, socalled perfect signals are usually employed at; the sending end of the circuit and the lengthening orif shortening of these signals due to imperfections ofthe circuit'is measured at the receiving end. These measurements are sometimes made at several speeds and, ina'ddition, a measurement may be made with a speed-of-failure meter. A fairly complete picture of the quality of transmission afforded by the circuit when perfectsignals are impressed at the sen-ding end,-may be obtained by such methods; However, in many cases in practice, particularly where the circuit under testis merely part of a complicated network, the signals impressedare distorted; The primary object of the present invention is to provide a simple procedure for measuring thetelegraph transmission capabilitiesof a circuit with the impressed signals distorted by known amounts as well as'with perfect impressed signals. Another'object is to provide arrangements for testing with non-repeating printer signals of the sametype encountered in service as compared with using a repeating signal which in some cases is not as difficult to transmit." .Another object is to use in meas uring the receiving marg1ns,,a pr1nter re-.

ceiver of the same type used in service so as to obtain easily interpreted results as regards printer operation. Another object is to provide for testing the ability of receiving printer mechanisms to function on distorted line signals. Other features and objects of the invention will appear more fully fromthe detailed description thereof hereinafter given.'. j With reference to the distorted signals utilized in the arrangements of this invention, the question arises as to which component or components of distortion should be used. it is'pointed out that with this inventlon it is possible to provide suitable clrcuits for introducing' either'bias, characteristic'or forininedyamounts or -in v I amounts and measuring the effect thereof by weevi s. v s su use of undistorted signals inthat it affords a we: 'n b; 248,1617} f tuitous components or any combination of these into the signals to produce the type of distorted signal desired. 1 However, it is probiably mjore convenient to measurefa-nd to control blas than "elther "of the other two" comlso, blasus acommon causefof' ponents. poor transmission and is comparatively easy to correct for in the field operationof telegraph circuits. Accordingly, I in l the testing method and arrangements of this 'inve'ntion,

bias-is introduced into the signals to produce H the desired distorted type of signal utilized.

However, the signals may be. distorted by otherm'eans' I i 9 The telegraph transmission measuring method ofthe present invention in whichdistorted signals are used, involves introducing distortion into the signals either. in' predeten' a v asa distortion meas urlng set or atelegraph'prlnter. This'method has an advantage overmethods involvlng the direct indication of the margin; in transmission, i.e.,-of the ability e distorted signals. Inthe 'method of this'iin vention the distortion is-impre'ssedatthe sending end of the circuit in order to determ ne the margin 1n the clrcult. Determination of the margin in thecircuit' shows the permissible initial distortion. in signalsim gradually increasing 1.

.75 of the circuit to handle 7 5 pressed at the'sending end. Such a testing] method and its accompanyingresults are particularly desirable in multi-section circuits where the signals at the sending end of some of the sections or circuits are distorted due to transmission over previous sections. In other words, thetesting method of the invention makes, it readily possible to ascertain how much distortion maybe introduced in the sigi nals prior to being sent over the circuit before the'rec'eiving apparatus will fail properly function." t

The inventionmay be more fully understood. from the following description, to a gether-with the accompanying drawing, in

the figureof which is shown a circuit gram of a telegraph system to which tlie testing and: a current limiting resistance.

f denser 1s;brid'g'e d. across to round 0H the wave shape of the tery' ande grOuILd -Ififiy source of reversals may p I v V J These jacks are connected to the" operating winding 2 of a sending relay wh ch 1s.

method and apparatus of this invention are applicable. 1 p

In the drawing is shown a transmission line L interconnecting a transmitting and receiving station. At thetransmitting station is shown a portable testiset for use with the arrangements'of the invention. This test set includes the jacks J to J inclusive." Bat- J;..and.J- .A telegraph printer sending distributor may be connected tojack J 3 and'a of the usual polar type. 'Conne'ctedte the biasing Winding. f he sending .relajy s, a ver et1e.r;ee eteneet6 andtheljacksjJ and J to which: be connected, respectively, bjattery, ground'and a meten'. I

" i ywinding 2 is a i retardatlon co l Qonnected in series. with v A conthe winding The actionl 'of this, inductance and condenser is signals through 5 the relay. Win ing when. the circuit is opened andclosed by the printer sending contactswhicli may be connected. ie jack J3.

WhenIrOiindedJ ofi signals are sent: through winding 2; signals with bias varying from about (w per center more spacing to 66per cent or more'm rk may b'e obtained from the relay contacts. by varying the direct curr I i lt- Q ngI hrOughbiasing winding 3b) changing, the variable resistance .6.

sending relay contacts The are connected to the and J LA meter may loe; connected t w Jeen -th P eP-e connected to'xa. lin 'ir tL may b onnectecltoijack J line circuit 11 is connected' t'othe windof receiving. re ay 4. The contact of receiving relay 4 contr0ls a circuitthr ough thedistortion"measuringset 5 ere receiving I paste, :1:

he" distortion; measuring set: 5 is well 'knownin the art and is {more completely illustrated 1n schematic form herein,

'' .ce v'ing printer arrangements are also Well known in the art.)

The testing method (5i tiiie ventifie the purpose .Of which i to determine the marg n in the i e introduced in the signals at the transmit ting's'tation before the receiving station will fail to properly runetioims asjtollowsi A source of revereal'g er' perfeet signals; ma be -connected to jack J; and th'e'biasin'g' current adjusted so that tliemeter' Mg'plu'gged into jack J will indicate perfect signals with the line plug removed from jack Je. "Then the line willbe connected in jack J and thesesignals transmitted over the line L. A

' readingavill then be takenon the distortion measuring sete5, or, the receiving printer. This will show the amount of distortion inbe connectedii to j acks' b n ct to j ekj.

; While, the invention has certain specific arrangements which are Loihow much distortion' may creased until the aieteraefi meeeerieg eet 5 or the receiving" printer"inclicates that the maximum amount or limit has 'been reached at whichthe receiver wiirprdpeny function. The distortion lneasuring set 5 will indicate the percent offdi'stortion or bias in the signals. For purposes of illustration, let it be assumed that it has been determined bytepr; periment' that with ee cent; distortion; as shown by set 5, the signals will operate receiver will not do, so beyond Accordingly, the biasli l gradually Qincreased at the sending statiomuntilndevice 5 gives an indication of such limit, thena reading of .thebias introduced at the; sending end-at? suh ti wil site a r ct ind c tion the margln' x i f l afq lfi e smitting distorted signals; The limit reet e' amount of distortion at theiiiiivirige end mayhe p v y. fit hii XPB -inln and differ for various types of signals. 1 WQ S; the e i Q P 1 d sto io tha m ual s gn als mig St d. m g t b d f e ent hem that the cas e lo f printer signals.

The ;testing method also-be slightly em te 3 T bi i fl e rl if l l i lyl n a me am U ni h intre i ion i he of a fixed andknowhiamount-of bias reading, would betaken on distortion ineasfueieee et-efie A. e mrieri le aof this e d wi h, t e known max mum lii ifi: n p rcen would make it easily possibleto estimate hovt much more, or lessfthan the fixrdand'arbitrary amount of b iasQmight b'e introduced,uand

would'indicate directly the margins ifor'trans mitting Si nals impressed with thelkn'own amountofbias; i

deemeddesirable; it is understood that it is capable of embodiment in many and other widely' varied ferrns'without departing item the spirit of the invention; as defined by the appended eieaifie; 7

What'iscla'imedis'i V f 1., e met e ofjtesting transmission in e telegraph circuit interconnecting e teat-e:

it i g anda.r ceiYing stat on Which coin-*- prises introducing distortioiratthe sending been disclosedji'fi station into the signals transmitted over said line n' easurmg the percentage of i distortion n such signals at the receiving station, and

comparing this measurement and the amount f, or ie nt-red ed I wit ee newe Vuring the distortion in said signals as reprinter signals over said maximum percentage of allowable distortion for such signals. 7

2. The method of testing transmission in a telegraph circuit interconnecting a transmitting and a receiving station which com prises introducing distortion at the sending station into the signals transmitted over said line, measuring the percentage of distortion in said signals at the receiver station, gradually increasing said introduced distortion until said measurements indicate the known maximum percentage of allowable distortion for such signals,- and measuring' station said distortion as at said sending.

in sald slgnals at said sendfinally introduced ing station.

3. The method of testing transmission in a telegraph system whichcomprises introducing an arbitrary amount of distortion into the signals sent over said system and measceived.

4. The method of testing transmission in a telegraph circuit interconnecting a printing telegraph transmitter and a printing telegraph receiver which comprises transmitting circuit, introducing distortion into said signals at the transmitter station, gradually increasing said introduced distortion until errors begin to occur in said printing telegraph receiver, and measuring the amount of distortion as finally introduced. a l

, 5. The method of testing transmission in a telegraph circuit interconnecting a printing telegraph transmitter and a printing tele- 1 graph receiver which comprises transmitting printer signals over said circuit, introducing a fixed known amount of distortion in said uring the margin of reception ofsaid signals I by said printer at'the receiver station.

6. Telegraph testing apparatus including means for biasing telegraph signals and for measuring the introduced bias, comprising a source of reversals, a relay associated therewith, a biasing circuit for said relay, a circuit controlled by the contacts of said relay, and a meter included in said last mentioned circuit. In testimony whereof, we'have signed our names to this specification this 19th day of January, 1928. a

EDWARD F. WATSON. BURDETTE S. SlVEZEY. 

